It’s not unusual to extrude pipe with a lattice basket die, then feed the pipe through a succession of crosshead spiral-mandrel coating dies to add functional layers. What is unusual is that Battenfeld Extrusionstechnik GmbH (BEX) in Germany has combined a modified lattice basket with spiral-mandrel layers in one compact coextrusion head. BEX (represented here by American Maplan Corp., McPherson, Kan.) began building these “hybrid” coex pipe dies two years ago to provide greater control of die pressure and wall thickness for sophisticated pipe structures where the core and functional layers have very different flow properties. The first were dies for glass-reinforced PP pipe, which competes with peroxide-cured PEX-A pipe in hot-water plumbing. A tungsten-carbide-coated mandrel core for glass-filled PP is surrounded with two spiral-mandrel layers for PP coating. BEX’s largest hybrid die so far is for 800-mm, four-layer pipe, using its special VSI spiral-mandrel/lattice-basket die for the HMWPE core and three spiral mandrels for layers of PP coatings. (620) 241-6843 • www.maplan.com
823 South 81 Bypass McPherson, KS 67460
Phone (620) 241-6843 Fax (620) 241-2142
Editor PickSizing the Barrier Gap
Here’s a less complex way to properly size the barrier gap for barrier screws.